Pressure compensated thermostat



Dec. 2, 1947. s. A. GIBSON 2,431,801

' PRESSURE COMPENSATED THERNOSTAT Filed Jan. 11, 1944 2 Sheets-Sheet 1 l9 aeflraibs I.

Dec. 2, 1947. G|BSQN PRESSURE COMPENSATED THERMOSTAT Filed Jan. 11, 1944 2 Sheets-Sheet 2 Slew 14m, Gi i 672 1) 50 77.

Patented Dec. 2, .1947

UNITED "STATES PATENT OFFICE 8 Claims. 1

This invention relates to thermostats, in class 297, and especially to a pressure compensated thermostat; and while this invention was especially designed and used to actuate an electric switch in a heat-regulating system of an in- .cubator, it is useful for actuating various other controllers, for instance, sates or valves of fluid passages, etc.

One object of this invention is to provide a thermostatic device that includes means to automatically compensate for variations in atmospheric or other external fluid-pressure, so that the controller is actuated thereby at a substantially invariable heat-norm, for any predetermined adjustment, regardless of considerable changes in external pressure of air or other fluid that surrounds the heat-responsive bellows or element that expands and contracts in response to rise and fall of surrounding temperature.

Another object is to provide, in a device of this character, a very simple and comparatively inexpensive form of actuator in combination and cooperation with a very simple supporting frame which is flexible and provided with a very'simple adjusting or flexing means by which the actuator can be adjusted with respect to the electric switch or other controller that is also supported by and secured to the said frame.

A further object is to provide, in a device of this kind, a knife-edged fulcrum in cooperation with said actuator and frame, this fulcrum being clamped on the frame and movable to different contact points along the lever that forms a part of the actuator, thereby to compensate for various average air-pressures, as at different altitudes where these devices may be installed for use and operation.

A further object is to provide, in a modified form of the inventioman arrangement in which the pressure-responsive bellows serves as a fulcrum of the lever to which it is attached and to which the heat-responsive bellows is also attached, thereby dispensing with the fulcrum previously described.

Another object is to provide, in a device of this character, an actuator whose heat-responsive bellows projects from one side of an end-portion of the lever to which it is secured, and whose pressure-responsive bellows projects from the opposite side at the opposite end of said lever, so that the atmospheric or outer pressure on the heat-responsive bellows is counteracted or counterbalanced by the equivalent outer pressure on the pressure-responsive bellows.

Other objects and important features are point- 2 ed out or implied in the following details of description; but before proceeding with the details, it should be understood that the Wafers" herewith shown are considered as one form of bellows, so this latter term is chosen as a broad term applicable to any form of fluid-filled expansible and contractable element; and'while, for purpose of distinction, one of these elements is specified as heat-responsive, and the other as pressure-responsive, both are somewhat responsive to both heat and pressure, so the distinction is mainly in the different degrees of response to heat and to pressure, as will become apparent from the following.

In the accompanying drawings, two forms of the invention are shown as follows:

Fig. 1 is a side elevation of one form of the in vention as installed on the roof or ceiling of a container, for instance, an incubator, the ceiling being shown in section.

Fig. 2 is a bottom plan in Fig. 1.

Fig. 3 is a transverse vertical sectional view taken along the lines 3-3, 3-3 of Figs. 1 and 2.

Fi 4 is a side elevation of a modifled form in which the combination involves a rearrangement of parts and an inversion of the whole, also an elimination of a special fulcrum such as in Figs. 1. 2 and 3.

Fig. 5 is a top plan view of the device shown in Fig. 3.

Fig. 6 is a transverse vertical sectional view taken along the lines ll, 8-8 of Figs. 4 and 5.

Referring to these drawings in detail, in which, similar reference numerals refer to similar parts in the several views, the invention is described in detail as follows:

In each form of the invention, the frame I0 is of the same shape and construction, being principally a bar of metal or other appropriate somewhat flexible and springy material bent into U- shape and having a supporting hanger or leg Illa welded or otherwise secured thereon, and a second, leg or hanger lob formed integrally with one of the two spaced and substantially parallel bars We and ltd, these being united by an intermediate frame-section Me. These bars lllc and Ind are apertured at If and lllg to receive an adjustin screw ll, while a concavity lllh is provided to receive a cylindrical nut ii. The screw Ii has a shoulder Ila that bears on the bar I00 and cooperates with the nut II for adjusting the bars I00 and lid with respect to one another for a purpose presently explained.

The controller or electric switch mechanism 13 view of the device shown heat-responsive wafers.

is secured on the frame ll, either in the fixed position and by means shown in Fig. 1, or in the adjustable position and by the clamping means shown in Fig. 4, according to arrangement of the other elements of the combination.

The actuating unit or actuator, in both forms of the invention, is a unitary structure that comprises a lever I 4, a bellows II or Ila that is filled with air or other highly compressible fluid that has slight heat-expansion, and a bellows Il or Ila that is filled with any appropriate fiuid that has a relatively high heat-expansion, these two bellows (in Figs. 1-3) being preferably the same size and construction. of the single wafer type;

but, because of the difference in their fillings, the bellows II is designated as the pressure-responsive bellows, and the bellows Il is designated as heat-responsive bellows. As seen in.1igs. 1 and 4, the pressure-responsive bellows is at one end and projects from one side of the lever I I, and the heat-responsive bellows is at the opposite end and projects from the opposite side of the lever I4; but in Fig. 4, I have shown each bellows of the dual-wafer type, mainly to show that the invention is not limited to any specific type, and these dual-wafer bellows are designated Ila for the pressure-responsive wafers and Ila for the Each bellows has oppositely projecting axial boxes that are respectively secured to the lever Il and frame ll of the modified form of Fig. 4: but in Fig. 1, a boss of only the pressure-responsive bellows II is secured to the frame ll, while th free boss of the heat-responsive bellows II is substantially against the outer end of the plunger Ila, so that the slightest expansion of the bellows Il will actuate the switch or controller II, this being true because of the cooperation of the fulcrum I'I whose knife-edge is against the intermediate portion of the lever ll, at or near the center of-the latter. This fulcrum is provided with a clamp ll that clamps the frame-bar Ild and can be loosened and moved rightward or leftward along the lever I4 to compensate for differences of average atmospheric pressures, at different altitudes where the device is installed, or to compensate for any difference in sensitiveness or responsiveness of the solid material of these wafers or bellows II and Il.

In forming the springy frame Il, when bent to the form shown, or approximately thereto, then released from the bending device (not shown), its bars I00 and Ild are then somewhat divergent from the element Ile; so, when the screw II is operated to draw them into the parallel relation shown, they continually tend to diverge, thereby exerting a pressure against the shoulder Ila and against the screw-threads, thereby frictionally securing the screw II in any one of its infinite number of micrometric adiustments; and now, assuming that the device is operating at too low a temperature when adjusted as shown in the drawings, the operating temperature can be raised, or the device can be adjusted for any appropriate higher operating temperature by simply unscrewing the screw II to the proper extent, thereby permitting the inherent springiness of the frame Il to lower the fulcrum I I, lever I4 and wafer or bellows Il, so a greater expansion of the latter will be required to actuate the controller Il. The purpose of the screw or adjusting means IIb (Fig. 4) is the same as that of screw II, except that when unscrewed, it lowers the frame-bar Ilc or permits the frameabar' Illd to raise the lever I4 away from the controller Il whose controlling element 9 is shown 4 in contact with the middle portion of the lever I4. Clamp Ila (Figs. 4-6) embraces the frame-bar I00, and can be loosened to permit the controller II to be slid along the bar IIic for positioning the controller-element Ila at any appropriate adjustment with respect to the lever I4.

Each bellows has an axial stud ll extending thru and secured in one of the two openings in the lever I4; and each bellows, except No. 16 has a stud II that extends thru and is secured in an opening of the frame ii.

The fulcrum I1 is provided with abutments Ila that project upward near the edges of the lever I4 and cooperate with the studs I9 and 20 of the bellows ll for keeping the central portion of the bellows iii in a proper operative relation to the element Ila.

Though I have described these embodiments of my invention quite specifically, I have no intention to limit my patent-protection to these precise details of construction and arrangement, for the invention is susceptible of numerous changes within the scope of the inventive ideas as implied and claimed. 1

I claim the following as my invention:

1. A heat-and-pressure-controlled actuator comprising a lever, a pressure-responsive bellows that includes a filling of compressible fluid that has a low coeflicient of heat expansion and is secured to and projects laterally from one side of an end-portion of said lever, and a heat-responsive bellows that includes a filling of fluid that has a high coefficient of heat expansion and is secured to and projects laterally from said lever at theside and end-portion opposite to the side and end-portion from which the pressure-responsive bellows projects; in combination with a frame adapted to have a controller secured thereon, said actuator being secured to said frame in a proper relation to cooperate with said frame for actuating said controller when the latter is secured to said frame in a proper position.

2. The combination defined by claim 1, said frame comprising a bar which is normally adapted to have said controller secured thereon, said frame comprising a second bar at a distance from the first-said bar and having one of said bellows secured thereto, and means to adjust one of said bars with respect to the other one of said bars and thereby adjust said actuator with respect to said controller when the latter is secured on the first-said bar.

'3.'The combination defined by claim 1, said frame comprising a bar which is adapted to have said controller secured thereon, said frame comprising a second bar on which one of said bellows is secured, and a fulcrum on and adjustable along said second bar and in cooperative contact with said lever at one of various points of adjustment between said pressure-responsive bellows and heat-responsive bellows.

4. The combination defined by claim 1, said frame comprising a bar which is adapted to have said controller secured thereon, said frame comprising a second baron which is secured one of said bellows, means to adjust one of said bars with respect to the other one of said bars and thereby adjust. said actuator with respect to distances betweensaid bars, and a fulcrum on and adjustable along one of said bars and in cooperative contact with said lever at one of various adjustment positions between said pressure-responsive bellows and said heat-responsive bellows.

5. The combination defined by claim 1, said frame comprising a bar which is adapted to have said controller secured tiibreon, said frame comprising a second bar having one end oi said prespressure-responsive bellows and heateresponsive bellows where it is in cooperative relation with said lever and pressure-responsive bellows for automatically regulating distances between said heat-responsive bellows and said controller when the latter is secured on the first-said par, and manually operable means to adjust the said bars with respect to one another and thereby cooperate with said lever to manually adjust said heatresponsive bellows bodily at various distances from said controller when the latter is secured on the first-said bar.

6. In the combination defined by claim 1, said frame comprising a bar, one of said bellows being secured on said bar, said frame comprising a second bar on-which is secured the other one of said bellows in a proper relation to support said lever between the first-said and second-said bars and in such position that the middle portion oi said lever constitutes means movable to and from a position for actuating said controller when the latter is secured on the first-said bar.

7. In the combination defined by claim 1, said frame comprising a bar adapted to have said controller secured thereon, one of said bellows being secured on said bar, said frame comprising a second bar on which is secured the other one of said bellows in a proper relation to support said lever between the first-said and second-said bars and in a proper position to constitute means movable to and from position to actuate said controller when the latter is secured on the first-said bar.

and means manually operable to adjust said bars and thereby adjust said leve with respect to said cured one of said bellows and which is adapted to have said controller-secured thereon, said frame comprising a second bar on which is secured the other one of said bellows in a proper relation to cooperate with the first-said bellows in supporting said lever between the first-said bar and second-said bar and in such position that said leverconstitutes means movable for actuating said controller whenthelatter .is secured on the first-said bar, and clamping means for movably securing said controller on the first-said bar so said controller can be adjusted along said lever for contact with'various points along said lever so as to compensate for various normal or average air-pressures on said pressure-responsive bellows.

' a GEORGE A. GIBSON.

REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS I Number France Dec: 13 1912 

